The invention relates to a switching input circuit having a stage of the emitter coupled logic (ECL) type having two transistors, the first receiving on its base an input signal and the second receiving on its base a control signal which is generated by a control circuit from the signal from the collector of the first transistor, in order to obtain on the collector of the second transistor an output signal switching faster than the input signal.
Such a circuit, generally used in order to compensate for the slowing down in switching due to highly capacitive input lines, is known from the MOTOROLA publication "Microelectronic Cell Data Book", the control signal consisting of a simple resistive divider bridge between the collector of the first transistor, the base of the second transistor and ground. When, for example, the voltage E changes from a low state to a high state, the putting into conduction of the first transistor causes the lowering of the voltage on the base of the second transistor, which accelerates the switching. This phenomenon is the same, in the opposite direction, for a transition of the signal E from a high state to a low state. The direct dependence between the control voltage and the signal from the collector of the first transistor means that it is not possible to select all of the operating parameters.